Wireless Sensor Networks (WSNs) are wireless networks of spatially distributed autonomous devices (called sensor nodes) that use sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion, pollutants, or comparable phenomena at different locations. WSNs are utilized in many application areas including environment and habitat monitoring, healthcare applications, factory automation, home automation, traffic control, and similar areas.
In addition to one or more sensors, each node in a sensor network is typically equipped with a radio transceiver or other wireless communication device, a low-power processor, and an energy source, usually a battery. The nodes of a WSN usually form a multi-hop communication mesh meaning that the intermediate nodes are used to forward data packets on the route from a source to a destination. Size and cost constraints on sensor nodes result in corresponding constraints on resources such as energy, memory, computational power, and bandwidth.
Nowadays a majority of the produced sensor nodes are equipped with low power radios such as IEEE 802.15.4 compliant radios. WSNs are often deployed in places where they have to share the radio frequency (RF) spectrum with other devices that may be using different technologies but the same RF band for data transferring. In the case of the IEEE 802.15.4 radio standard, the sensor nodes use the 2.4 GHz ISM (Industrial, Scientific and Medical) band also exploited by other radio standards such as 802.11a/b/g and Bluetooth®. The function and performance of the WSN can be harmfully influenced by more powerful near-by devices operating in the same radio frequency range.